1. Field of Disclosure
The present disclosure of invention relates to electrophoretic display devices, and more particularly to electrophoretic display devices structured to provide improved color gamut.
2. Technology Background
With rapid developments in the information age, information display devices have increasingly been used in a broad range of applications. Information display devices may include a liquid crystal display (“LCD”) devices, electrophoretic display (“EPD”) devices, plasma display panels, etc., which are connected to a digital computer or another source of image data.
In particular, the EPD device may be characterized as having high reflectivity and a high contrast ratio, and in distinction to conventional LCD devices, having no substantial limit as to user viewing angle. Accordingly, a user may experience the EPD device as displaying images as if it displays the images on paper. Unlike an LCD device, the EPD device does not require a polarizing plate, an alignment layer, liquid crystal, etc, where the latter result in increased costs and manufacturing complexities.
The conventional EPD device includes an electrophoretic layer containing microcapsules or barrier-type microcups in which white and black particles (or otherwise differently reflecting and absorbing particles) of respectively opposed electrical charge are formed. The charged particles move up and down so as to be more reflective on top (to display white) or to be more absorptive on top (to display a dark or black image are). Older EPD devices did not display various colors, just black and white areas. These older devices thus had difficulty in expressing much information with use of only black and white coloration. Although some newer EPD devices sport a structure in which plural color filters of different colorations are formed over the black-versus-white (absorptive versus reflective) electrophoretic layer regions, these devices suffer from lowered luminance because the amount of light (e.g., ambient light) that is reflected back to the user's eyes is substantially lowered due to all of the light passing through the color filters. Furthermore, an undesired color mixture effect may be generated due to misalignment of the color filters relative to a lower substrate that contains TFT-controlled pixel areas. The result is decreased luminance and reduced color gamut (ability of the display to display a full gamut of distinct colors).